This invention relates generally to inflatable restraint systems and, more particularly, to specifically sized airbag inflators and to airbag module assemblies containing such specifically sized airbag inflators.
Airbag module assemblies generally include, as basic components: 1) an airbag cushion, which is rapidly inflated when the vehicle encounters sudden deceleration, 2) an inflator, which upon actuation serves to provide an inflation fluid, e.g., a gas, used to inflate the airbag cushion, and 3) a reaction canister, which typically functions as a structural housing supporting assembly components such as the airbag cushion and the inflator, for example, while providing a mounting base for installation of the assembly in a vehicle and serving to direct the inflation fluid resulting from the inflator.
Safety restraint airbag cushions are normally sized and shaped to provide a vehicle occupant with desired cushioning protection when one or more airbag cushions have been properly deployed. In airbag module assemblies, airbag cushions are typically stored within a reaction canister in an uninflated, folded condition. In practice, reaction canisters which contain an airbag cushion for the protection of a front seat passenger commonly have a rectangular cross sectional shape and form a correspondingly shaped opening wherethrough the airbag cushion is deployable. Normally, a passenger side airbag module assembly is mounted in or behind what is called the vehicle instrument panel or dashboard (hereinafter referred to as the "instrument panel"), with the airbag deployment opening of the reaction canister positioned planar or adjacent the instrument panel.
The size of the airbag deployment opening, e.g., the length and width of the rectangular shaped opening, are normally determined by the need to provide a particular desired airbag cushion deployment. Thus, it is common that reaction canisters have a length predetermined by the size of the inflatable airbag cushion which is to be housed therein.
In typical passenger side airbag module assemblies, the inflator has a generally hollow outer housing structure, which is generally of an elongated cylindrical shape. One type of commonly used inflator device contains a load of a gas generant material stored within such an inflator housing structure. The size of the gas generant load is generally predetermined in order to be sufficient to result in desired inflation of the associated airbag cushion upon actuation of the inflator.
In practice, such inflators are commonly sized dependent upon the shape and size of the corresponding reaction canister. For example, such inflator devices typically have a cylindrical diameter predetermined to permit the inflator to be housed within the reaction canister and a longitudinal length selected to correspond to that of the respective reaction canister. The sizing of an inflator device to correspond to the size of a corresponding reaction canister, however, can result in the inflator device outer structure having an inner volume which is larger than needed for the storage of the predetermined load of a gas generant material sufficient to result in desired inflation of the airbag cushion upon actuation of the inflator. Such extra or added volume is sometimes simply referred to as "free volume." In order to at least in part compensate for the presence of such free volume, it is common that such inflator devices include one or more variously sized and shaped internal elements, sometimes simply referred to as "spacers."
Unfortunately, the presence of free volume within an inflator structure can result in the inflator having less than optimal performance or design. For example, the presence of such free volume within an inflator structure can detrimentally increase the volume of the inflator cavity which must be pressurized in order for the inflator to achieve a proper combustion of the stored gas generant material. Additionally, as a result of such increased internal volume, an inflator may experience an undesirable delay in attaining proper combustion and may produce an effluent with a greater than desired particulate content.
Further, the presence of such unnecessary volume within an airbag module assembly component can undesirably result in the module assembly being larger than needed or desired.
Still further, larger than desired module assemblies can be more costly to manufacture, assemble and produce and may unduly or unnecessarily limit the range of module design variation and placement within a vehicle.
Thus, there is a need and a demand for an airbag module assembly which reduces, minimizes or avoids problems normally associated with the inclusion of free volume, in a relatively large amount, within an associated inflator device.
Further, there is a need and a demand for an airbag module assembly of more compact and lighter weight design.
Still further, there is a need and a demand for an airbag module assembly, particularly for the passenger side of a vehicle, having an improved design and more consistent performance.